Combustible Dust Explosion Protection: Flameless Venting

As a pioneer in developing explosion venting systems, REMBE® has fundamentally changed the world of explosion protection.  Since the invention of the Q-Rohr over 30 years ago, REMBE® has pushed flameless vents to their limits. This has led to the development of a family of flameless vents that satisfy multiple applications across many industries. Whether you are working with metal dusts, gaseous mixtures, vibrating equipment, high Kst values, or anything in between, we have a flameless vent solution for you. When used in combination with our other certified protection, plant equipment, buildings and employees will remain safe from a combustible dust explosion.

How do they work?

Heat generated from a combustible dust explosion can reach temperatures of 3000° F and flames can expand out to 200 feet. This blast wave can be catastrophic if vented inside a facility creating an even more intense secondary explosion. To solve this hazard, a flameless    vent can be used to safely vent the explosion indoors.

Flameless vents incorporate a standard explosion panel on the bottom which opens at a specific burst pressure, but the explosion is prevented from firing outwards.  Flames are cooled very efficiently by energy dissipation due to the    special stainless-steel mesh inset developed specifically for the flameless vents. This woven metal mesh inset reduces the volume of the escaping heat and extinguishes the flame. It also acts as a particulate retention device so no hot embers are released. In addition, the typical pressure and noise increase from an event are reduced to a barely perceptible level. Flameless venting systems provide the optimum protection against both the explosion and its potential consequences.

All flameless vents are mounted using standard flanges. No special training or knowledge is required and the venting system can be installed in just a few minutes. Installation of a replacement panel after an explosion is equally quick, which significantly reduces the resulting production downtime.

A visual overview of the REMBE® Q-Rohr®:

Due to the popularity of this venting style, REMBE has developed multiple flameless venting devices. There are now several unique designs that can handle almost any type of combustible dust/gas application. These designs are categorized into three primary styles: the Q-Rohr-3, the Q-Box, and the Q-Ball. Each has its own purpose and advantages which allows us to provide a quality engineered solution for any project.


The REMBE® Q-Rohr® is the evolved version of the original flameless venting system invented over 30 years ago. The robust design was built to handle intense explosions. This base style can handle Kst values up to 400 bar m/s and a Pred of 2.0 bar while effectively containing the explosion. This ATEX certified, NFPA compliant device provides excellent protection for organic dust, hybrid mixtures, melting dusts, and fibers. Even with this versatility, there are still other applications that require a different design.

Q-Rohr® for metal dusts

Working with customers and their processes, REMBE® identified a need for protection against combustible metal dust. In metal dust applications, the combustion temperatures and thermal energy can far exceed those of other types of dust. In the event of an explosion, the temperature can reach approximately 5400 °F (3000 °C) and can cause devastating damage when combined with the sudden pressure wave. Explosion safety for companies in the metalworking industry is difficult and expensive, especially for equipment used indoors. Until recently, most companies in this sector have used wet separators to prevent explosions. However, the resulting sludge is not only difficult to handle, but also expensive to dispose of correctly.

With these considerations in mind, REMBE® developed a new design, the Q-Rohr®-for metal dust. This new model is the first ever flameless vent certified for metal dust explosions. It can handle Kst values up to 300 bar m/s as well as aluminum dust explosions in the AL version. Companies can now focus on finding optimal plant layouts for their specific production processes instead of installing equipment outdoors.

Q-Rohr® for gas applications

While the primary concern comes from combustible dusts, there are still gas type applications that require protection solutions. For this reason, we developed a specific model that is tested and certified to handle gaseous type explosions. This specific model can handle propane level explosions and go up to diameters of over four and half feet!

Q-Rohr® DFE for gas-fueled engines

This newer flameless venting variation by REMBE® stems from a new situation developing across the globe. Increased development of renewable energy power plants has resulted in a reduction of CO2 emissions, the shutdown of coal-fired power plants, and the decommissioning of nuclear power stations.

But this dramatic shift in energy production also requires solutions that guarantee the continuous availability of an energy supply. The output of wind and solar plants are not constant. When these do not fulfill energy requirements, other sources, such as gas-fired power stations, must make up the difference.

An incorrectly functioning gas-fueled power station might allow a flammable mixture to occur in the exhaust system. In the worst-case scenario, an explosion could occur that not only damages the power station, but also creates a serious risk to personnel in the generator building. Energy production and emergency power supplies would be out of action for an extended period. This unplanned stoppage of gas-fueled power stations would pose a significant threat to the stability of the electricity grid and energy supply security.

Working with its energy partners, REMBE® developed a solution that can safely protect these engines indoors. This model of the Q-Rohr® DFE allows for power companies to safely run gas-fired generators without the need for expensive protection solutions. If an explosion occurs, neither flames nor a pressure wave would emerge from the vessel. This reduces downtimes to a minimum and increases power plant availability.

Q-Rohr® DFE for dual-fueled engines

As of 2020, the next phase of the IMO emission regulations for shipping reduces the permitted sulfur and nitrogen content of fuel from 3.5 % to 0.5 %. Due to the IMO tier 2 and 3 regulations, shipping will increasingly be required to use alternative sources of propulsion such as dual-fuel engines and LNG-powered plants.

If a fault occurs in the engines’ exhaust system, a potential flammable mixture could develop leading to an explosion. The result would be a failure of the drive system and electrical power supply. Essential instruments such as radios, radar, and navigation equipment could be adversely affected. In addition, exploding sections of the plant would create a serious risk of injury to personnel in the engine room.

Preparing for this shift in 2020, REMBE® developed another model of the Q-Rohr DFE for these dual-fueled engines. This model has maritime class certification in accordance with DNV-GL, LR, BV, and ABS. Its design is perfect for flameless venting in the ship’s hull while allowing for a quick restart when operations are safe.


While the Q-Rohr® and its many variations are great protection devices, the robust design is not needed for all applications.  This led to the invention of the Q-Box for less complex processes and/or products with lower Kst values. The Q-Box can handle many common combustible organic dust, melting dust, and abrasive dust and is certified for Kst values up to 200 bar m/s making, it perfect for wood and food/agricultural industries. It can be used on equipment such as filters, conveyors, silos, and everything in between. This versatility makes it the most common flameless vent. Its unique quarter-circle design can be seen below.


The latest flameless vent to be invented is the Q-Ball®. The Q-Ball® was developed with a unique full-body venting design in order to be the most efficient flameless vent. This design means that a lower quantity of units could be used for a given application. Additionally, this efficient cooling inside the Q-Ball prevents flames from escaping and minimizes the effects of the explosion pressure to an insignificant level. It was designed for two applications, bucket elevators and oscillating/vibrating equipment.

Q-Ball® E

This model is suitable for flameless venting of mechanical conveyors such as bucket elevators, belt conveyors, drag conveyors, etc. It can handle explosions with Kst values up to 200 bar m/s making it useful for almost all conveyor applications. The Q-Ball® E is available in multiple sizes to match most standard conveyors and elevators. Additionally, the low weight of the Q-Ball® E reduces the need to reinforce the elevator supports. These features make installation relatively easy.

Q-Ball® S

Unlike conventional flameless explosion venting devices, the Q-Ball® S was specifically developed for oscillating and vibrating plant components such as screeners. It can handle Kst values up to 265 bar m/s, making it very versatile.  A uniquely designed substructure and low weight allows the Q-Ball® S to be attached directly to the oscillating system without costly extensions or conversions. The Q-Bal S ensures maximum venting efficiency so the required venting area can be reduced to a minimum.

Which is right for you?

With so many options for flameless vents, REMBE® Inc. can develop an engineered solution for your process requirements. Flameless venting is extremely versatile and can be the optimal protection design in many applications. For this reason, REMBE® continues to develop this technology beyond the scope of other offerings currently in the market.

Here is a recap of some of the benefits:

  • The production process can remain safely indoors and does not have to be near an external wall.
  • The only maintenance required is an annual visual inspection.
  • There is an integrated signaling unit that is prewired to the unit for reliable monitoring.
  • They reduce the noise level and pressure rise typically associated with explosions to an acceptable level.
  • The recoil force is reduced by half of a standard vented explosion.
  • They can be used indoors or outdoors.
  • They are excellent for retrofit applications and can be less expensive than external vent ducts.
  • The maximum exhaust temperature is approximately 140 °F (60 °C) for less than 1 second
  • The maximum external pressure increase will not exceed 5 mbar

About  REMBE®:

For over 50 years, REMBE® has been and continues to be a leader in the innovation and manufacture of high-quality process safety systems, explosion protection systems and dynamic weighing systems

REMBE stands for expertise in explosion safety and pressure relief, providing customers in virtually every industry with safety systems for their plants and equipment. All products meet the requirements of national and international regulations, include ATEX and NFPA.

REMBE® customers include market leaders in numerous sectors, such as the oil and gas, food, wood, chemical, pharmaceutical and petrochemical industries.

REMBE takes a comprehensive approach, developing and manufacturing its own products while also providing the relevant consulting, engineering and service to meet your needs.

  • As the inventor of flameless venting, REMBE® specializes in combustible dust explosion prevention/protection systems for many applications across a multitude of industries with a deep product selection of both venting and isolation devices.
  • REMBE® has led the process safety industry with new, more adaptable rupture disc products to address ever‐changing, complex needs.
  • The C‐LEVER dynamic weighing system provides a reliable, easy‐to-use-and-maintain option for continuous weighing.

Contact REMBE® Inc. today, 704.716.7022, or to speak to an Engineer about your combustible dust explosion isolation application today and we will recommend the best product system for your needs.

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